The present invention relates to controlling optimum write power, and more particularly, to a method and optical disc drive capable of utilizing an inflection point of a characteristic curve of writing quality parameters to write powers to determine the optimum write power.
More recently, writable optical disc drives, such as common DVD-R/RW, DVD+R/RW, or DVD-RAM drives, for use with computer systems, have become widely available to individuals. As a result, the need to improve performance of these devices has increased considerably.
Generally, determining the optimum write power of above drives requires an optimum power control (OPC) procedure before data recording or a running optimum power control (ROPC) procedure during the data recording. As to the OPC procedure, many related art methods are utilized to determine the optimum write power. Please refer to FIG. 1. FIG. 1 is a diagram illustrating two characteristic curves, C1 and C2, of reflection difference M14 to write power according to the related art. As defined in optical disc specifications, M14 represents the reflection difference between a 14T pit and 14T land. M14 is the maximum amplitude of vibration in the RF signal. Therefore, a characteristic curve of reflection difference M14 and write power can be used to determine the optimum write power. As shown in FIG. 1, the characteristic curve C1 has a saturation region and a point A1 at the saturation region. Therefore, for an optical disc having a characteristic curve M1, a write power PS, associated with the point A1 and close to the optimum write power PO, is accordingly determined to be the write power used for recording data. Assume the inserted optical disc corresponds to the characteristic curve C2 shown in FIG. 1. It is clear that the characteristic curve C2 has no saturation region. Using the reflection difference M14 fails to obtain suitable write power applied for recording user data to an optical disc having the characteristic curve C2.
As known to those skilled in this art, if the found optimum write power is higher than a normal optimum write power applied to a rewritable optical disc, the allowable times of rewriting data to the rewritable optical disc are greatly reduced, shortening the rewritable optical disc's life. Therefore, how to properly find the desired optimum write power becomes an important issue for designers.